1. Field of the Invention
The present invention provides a projector, and more specially, to a projector capable of adjusting the screen size and luminance depending on various environments.
2. Description of the Prior Art
In conference briefings, the host can project the related materials or graphs on a screen with projectors to have the participants better understand the discussion. However, with the advance of video/audio equipment and storage media, such as high power stereos and large capacity DVDs, normal families can also enjoy the same real-time perceptive feeling as in a home theater through the extra-large screen projected from the projector with the combination of projectors and stereos, which makes the use of projectors gradually extend into normal families.
However, while the technology of optical engines and illuminating lightning goes further and further, the luminance which the projectors can achieve also gets stronger. However, power consumption becomes larger in the mean time. Yet, the operating environments and purposes often differ considerably; for example, the luminance of projectors required in briefings is stronger than that in families, and stronger luminance is needed in more open operating environments to grant the participants clearer vision. But the luminance of projectors mostly requires manual adjustment according to actual situation now, which is very inconvenient for users who are not familiar with the operation of projectors. Although there are some projectors, which can adjust its luminance automatically, such as the projector disclosed by Taiwan Patent No. 399742, which employs a photo diode to detect the ambient luminance of surroundings and according to which adjusts the luminance of projected beams automatically, such adjustment of the projector luminance according to the luminance detected by the diode is not correctly available because the luminance should change with the length of indoor space. For example, in spaces of large length, the projected luminance from projectors requires higher power to have the clear image on the screen. But, in spaces of shorter length, the projector only requires lower power for projected image with identical luminance. Therefore, the conventional projectors can only operate normally in spaces of specific fixed length but not correctly adjust projecting power with different indoor spaces. Besides, conventional projectors cannot calculate the position at which the projector should be arranged depending on indoor spaces, and notify the users how to adjust the position, either. Consequently, the users can only set up the projectors with personal subjective feelings, resulting in inexact arrangement position of the projector in indoor space.